class_docstr: Extends the observer LogReturns to show two instruments
code: def next(self):
      super(LogReturns2, self).next()
      self.lines.logret2[0] = self.logret2.rets[self.logret2.dtkey]
  
file_path: backtrader/backtrader/observers/logreturns.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import backtrader
label_desc: Use image node_id 2 for calling the LogReturns2 obj's underlying member method code with example usage: obj.next() without return types